Severe hypoplastic crisis among patients with sickle cell anemia has been associated with infection with what appears to be a non-cultivatable parvovirus-like agent. The presumed agent was first identified by the relatively insensitive counterelectrophoresis technique. The immune adherence hemagglutination technique has been adapted to identification of this agent and its antibody: approximately 60 percent of normal populations have been found to be antibody-positive. Attempts to transmit the serum parvovirus-like agent to primates and to isolate it in primary cultures of human bone marrow are in progress.